Psysical-chemical and biological testing of phytomeliorated rocks of the Pokrov land reclamation Station

The physical and chemical properties of the phytomeliorated overburden rocks of the Pokrov land reclamation station of the Nikopol manganese ore deposit and two types of technogenic substrates were studied: loess-like loam, red-brown clay, grey-green clay, dark-grey schist clay and black soils placed on layers of sand and loess-like loam. Samples were taken from each type of technosol at a depth of 10‒20 cm (plough layer) and 20‒40 cm (sub-plough layer). Identification of the suitability of these technosols for growing crops was carried out by phytotest method. It was revealed that the main clay mineral of dark-grey schist and red-brown clays is the illite. Grey-green clay predominantly consists of montmorillonite, and in loess-like loam and black soil, the content of kaolinite, illite and montmorillonite is more or less the same. The maximal hygroscopicity level was observed in grey-green clay (20.5%). The minimal level was fixed in red-brown clay (7.6%). Phytomeliorated mining rocks are weakly humus; the humus content in them does not exceed 1.25%. Technogenic substrates contain 2.5‒3.3% of humus and belong to low-humus soils. All studied technosols belong to slightly alkaline substrates in which the pH varies from 7.34 to 7.86 in the plough layer and from 6.6 to 7.91 in the sub-plough layer. In two of the investigated mining rocks (grey-green and dark-grey schist clays), weak sulfate-chloride salinity was observed. In grey-green clay, the concentration of soluble salts was increased both in plough layer (0.214%) and in the sub-plough layer (0.202%). In the dark-grey schist clay, salinity was observed only in the sub-plough layer, but it was stronger than in the grey-green clay (0.281%). The concentration of chlorides and sulfates in these technosols exceeded the toxicity threshold by 7‒8 and 1.5‒1.7 times, respectively. The sub-plough layer of dark-grey schist clay and both layers of grey-green clay are phytotoxic. The inhibitory action on the growth and development of plants is caused by the cumulative effect of a soil acid - base imbalance, salinity and low fertility of these technosols. Cultivation of agricultural plants on them is expedient and economically justified only under the condition of carrying out a number of meliorative measures aimed at improving the physical and chemical properties of these substrates.